Samsung's 850 EVO M.2 solid-state drive reviewed

Now available in fun-sized flavorsby Geoff Gasior  9:00 AM on March 31, 2015

When we reviewed Samsung's 850 EVO SSD last year, we commented on its remarkably compact internals. Although the drive comes in a standard 2.5" case, the underlying circuit board occupies a fraction of that footprint. It was only a matter of time before Samsung rolled out miniaturized versions designed for smaller mSATA and M.2 form factors. And here they are:

mSATA (left), M.2 (middle), and 2.5" (right) flavors of the 850 EVO

Apart from conforming to smaller form factors, the mini EVOs are identical to their full-sized siblings. They use the same 3D V-NAND with 32 layers and three bits per cell, and they accelerate writes with the same SLC caching scheme. They also use the same Samsung controllers. As in the 2.5" lineup, the 120-500GB versions have the latest MGX chip, while the 1TB sports MEX silicon from the 850 Pro. The dual-core MGX controller isn't as powerful as the triple-core MEX chip, but Samsung says it's fast enough to deliver full performance at lower capacities.

Both controllers have SATA interfaces, so they can't hook into the PCIe lanes available in some M.2 and mSATA slots. (mSATA shares a physical connector with mini PCIe cards.) The mini EVOs require slots with built-in SATA connectivity.

The 850 EVO mSATA scales all the way up to 1TB, while the M.2 tops out at 500GB. At only 80 mm long, the M.2 2280 "gumstick" apparently lacks the land mass to house 1TB of flash. The M.2 standard includes provisions for longer 22110 drives, so perhaps we'll see a super-sized option eventually.

Apart from a few minor differences, the mini EVOs have identical performance ratings to their full-sized counterparts. They have the same AES encryption support, complete with the TCG Opal and IEEE compliance required by Microsoft's eDrive spec. And they're covered by the same endurance ratings, which promise 70TB of total writes for the 120GB and 250GB drives and 150TB for the larger sizes. That works out to 39GB and 84GB per day, respectively, for the length of the five-year warranty. Which is an awful lot.

Most of the fun-sized 850 EVOs are already listed at Newegg. They're priced at a premium over the 2.5" alternatives, but that's also true of mSATA flavors of the old 840 EVO. With comparatively little competition in the mini SSD arena (at least among drives sold directly to consumers), prices tend to be a bit higher.

Since our original 850 EVO review already explores the drive's performance in great detail, there's no need to put the new family members through the wringer. We ran the 850 EVO M.2 250GB against its SATA counterpart in a handful of IOMeter tests and, well, see for yourself:

Clicking the buttons below the graphs switches between queue depths, but there's little point. The two drives perform almost identically in these sequential and random tests.

They shadow each other under sustained and scaling loads, as well.

So there you have it. Samsung has officially rolled out mini versions of the 850 EVO. The drives have smaller M.2 and mSATA form factors, and they're a little pricier than the 2.5" versions that have been circulating since late last year. But they're pretty much identical otherwise.

Users can look forward to strong all-around performance and low power consumption, which is a good combo for mobile and small-form-factor systems that require mini drives. Given the price premium and the lack of PCIe connectivity, though, there's little reason for folks with spare drive bays to downsize from the 2.5" original.